1. Field of the Invention
The present invention relates to an intake air flow regulator apparatus for use on an internal combustion engine. More particularly, the present invention relates to an air flow regulator apparatus in which a guide structure guides axial movement of an air flow regulator plug in response to movement of a throttle actuator, to control air flow through an intake passage and to a combustion chamber.
2. Description of the Background Art
Within an intake passage for introducing intake air into a combustion chamber of an internal combustion engine, a throttle valve, such as a butterfly-type rotary opening/closing valve is normally provided, for controlling the amount of intake air flowing therethrough. If a throttle valve is disposed within the intake passage, a limit is encountered in shortening the intake passage. Often in the conventional engine technology, this type of butterfly valve has been provided as part of a generally cylindrical throttle body.
Particularly, in the case of an internal combustion engine operating at a high rotary speed, it is necessary to shorten the length of an intake passage in order to obtain a high output. However, it is difficult to meet this requirement where the throttle valve is disposed within the intake passage.
Moreover, if a rotary opening/closing valve or the like is present within an intake passage, the air flow resistance increases, because the valve mechanism disturbs the smooth flow of intake air.
To avoid this inconvenience, an intake passage has been proposed which opens in a funnel shape into a surge tank, and an air guide member for conducting air into the air funnel is disposed at a position opposed to the opening of the air funnel, so as to be movable in an intake axis direction. The air guide member is actuated by a motor. Such an intake passage is disclosed, for example, in Japanese Laid-open Patent No. Hei 11-324832.
In Japanese Laid-open Patent No. Hei 11-324832, since the air guide member is not disposed within the intake passage, but instead, is disposed in opposition to the air funnel opening of the intake passage, it is possible to shorten the intake passage further than was previously possible, with little or no risk of disturbance of the intake air flow.
When the air guide member is close to the air funnel opening when the engine is operating in a low-revolution operation state, i.e., an operation state involving control of a very small amount of intake air, a negative pressure or vacuum within the intake passage is heavily imposed on the air guide member, and has a tendency to pull the air guide member towards the opening. As a result, a large amount of power is required for moving the air guide member, and thus it is not easy to control the amount of intake air.
Also when the air guide member is moved by a motor, as in Japanese Patent Laid-open No. Hei 11-324832, it is necessary to use a greater operating force than a high negative pressure imposed on the air guide member which is positioned in proximity to the air funnel opening. Accordingly, a motor of a relatively large power output is needed to move the air guide member, the required size and weight of the motor is larger, and the cost thereof increases.
The present invention has been accomplished in view of the above-mentioned points and it is an object of the invention to provide an intake flow control apparatus for use in an internal combustion engine having a shortened intake passage, thereby obtaining a high output, and permitting the light actuation of an air flow regulator in an engine operation state involving control of a very small amount of intake air, thereby facilitating control of the amount of intake air.
As discussed above, when controlling the amount of intake air throughout the whole of an operational range of an internal combustion engine, there is an operation region when the engine is operating in a low-revolution operation state, i.e., an operation state involving control of a very small amount of intake air. In such an operation region, an air guide member is positioned in close proximity to an intake passage opening. Therefore, it is preferable that a uniform clearance between the air guide member and the intake passage opening in such a close positional relation to each other be constant independently of disturbance.
When an air guide member is provided in a tank wall of a surge tank attached to an intake pipe as in Japanese Patent Laid-open No. Hei 11-324832, it is necessary, for keeping the aforesaid clearance constant, to ensure the accuracy of each component of the surge tank and the mounting accuracy of the tank.
Pulsation of a negative pressure acts on the air guide member. Therefore, in order for the air guide member and the intake passage opening to be constantly aligned with each other on the same intake axis, the surge tank itself is required to be highly rigid so as not to be influenced by pulsation of the negative pressure. However, when high rigidity is required for the surge tank, an excessive weight inevitably results.
The present invention has been accomplished in view of the above-mentioned point. It is an object of the invention to provide an intake flow control apparatus for an internal combustion engine which can shorten an intake passage to obtain a high output and which, with use of a simple and light-weight guide structure, can easily ensure a high movement position accuracy of an intake air control valve with respect to an intake passage opening, regardless of pressure disturbances.
The air guide member as an air flow regulator described in Japanese Patent Laid-open No. Hei 11-324832 is a single valve element. With manual operation, it is difficult to arbitrarily change the amount of intake air using a single valve element in accordance with the amount of a throttle operation.
Therefore, it is necessary to control air flow regulator operation with use of a motor or the like. However, when setting a basic valve angle characteristic of a valve element by controlling valve operation with use of a motor, complicated control is required.
The present invention has been accomplished in view of the above-mentioned point and in a particular embodiment hereof, the present invention provides an intake flow control apparatus for an internal combustion engine having a shortened intake passage, thereby obtaining a high output, and in which, even by manual operation or by a simple operation control using a motor or the like, a required intake air quantity characteristic relative to the amount of a throttle operation can be set easily.